Methods of Stabilizing the Sacroiliac Joint

ABSTRACT

Methods of stabilizing the sacroiliac joint by placing an expandable device in the joint to generate laterally opposing forces against the iliac and sacral surfaces of the SI joint to securely seat the device in a plane generally parallel to the SI joint. The expandable device is coated with or otherwise contains a bone material to promote fusion of the joint. The expandable device used in methods of the present invention can be, for example, an expandable cage, a balloon, a balloon-expandable stent or a self-expanding stent.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of U.S. patentapplication Ser. No. 11/871,621 filed on Oct. 12, 2007, which isincorporated in its entirety herein.

TECHNICAL FIELD

The present application is directed to various methods for stabilizingthe sacroiliac joint including via fusing the joint.

SUMMARY OF THE INVENTION

The sacroiliac (SI) joint is a diarthrodial joint that joins the sacrumto the pelvis. In this joint, hyaline cartilage on the sacral side movesagainst fibrocartilage on the iliac side. The joint is generally Cshaped with 2 lever arms that interlock at the second sacral level. Thejoint contains numerous ridges and depressions, indicating its functionfor stability more than motion. In fact, the SI joint's main functionappears to be providing shock absorption for the spine throughstretching in various directions. Stability in the SI joint is providedby the large ridges present in the joint and by the presence ofgenerously sized ligaments, which offer resistance to shear and loading.The deep anterior, posterior, and interosseous ligaments resist the loadof the sacrum relative to the ilium and the more superficial ligaments,such as the sacrotuberous ligament react to dynamic motions.

The human spinal column is configured so that the total weight of theupper body rests on the two small SI joints at the juncture of thesacrum and ilia. The stress placed on this area in the upright positionmakes the lower back susceptible to injury. In fact, one of the mostcommon causes of problems at the SI joint is an injury. The force fromsuch an injury can strain the ligaments around the joint potentiallycausing tearing which can lead to hypermobility in the joint. Suchhypermobility can eventually lead to wear and tear of the joint and painfrom degenerative arthritis. Injuries can also cause direct injury ofthe articular cartilage lining the joint, which too, over time, can leadto degenerative arthritis in the joint.

In some patients, SI joint pain occurs because of an abnormality of thesacrum bone itself. Before birth, several vertebra fuse together to formthe sacrum but in some patient populations, the bones that constitutethe sacrum never fuse together. In these cases, two or more of thevertebra that should fuse together remain separated, which can give riseto problems with the SI joint.

Furthermore, women may be at risk for developing SI joint problems laterin life due to childbirth since the long dorsal sacroiliac ligament canbecome stretched in periods of such reduced lumbar lordosis (i.e.pregnancy). Specifically, During pregnancy, hormones are released thatallow the connective tissues in the body to relax. The relaxation isnecessary so that during delivery, the female pelvis can stretch enoughto allow birth. However, this stretching can cause changes to the SIjoints, making them hypermobile. Over a period of years, these changescan eventually lead to wear-and-tear arthritis. As would be expected,the more pregnancies a woman has, the higher her chances of SI jointproblems.

Surgery on the SI joint usually consists of a fusion of the joint. An SIjoint fusion is performed by first making an incision over the SI jointin the lower back. The joint is opened so the surgeon can visualize theiliac and sacral surfaces of the SI joint. Once the joint surfaces arein clear view, the articular cartilage lining the joint is removed fromboth surfaces. The bone surfaces are then held together until theyactually heal together, or fuse. To hold the bones together, the surgeonwill usually insert several metal screws across the joint or a boneplate. This historically has been a large surgical procedure withoutgreat success.

Therefore, there is a need in the art for a minimally invasive devicethat provides for long term joint stability.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given hereinbelow and the accompanying drawingswhich are given by way of illustration only, and thus are not limitativeof the present invention, and wherein:

FIG. 1 is a schematic illustration of a device of the present inventionpositioned in the sacroiliac joint in an expanded, deployedconfiguration.

FIG. 2 is an exploded view of a device according to an embodiment of thepresent invention.

FIG. 3 is a cross-sectional view of a screw of a device according to anembodiment of the present invention.

FIG. 4 is a fragmentary perspective view of a screw of a deviceaccording to an embodiment of the present invention and a fragmentaryperspective view of an installation tool that can be used to rotate thescrew.

FIG. 5 is a perspective view of a locking nut of a device according toan embodiment of the present invention and a fragmentary perspectiveview of an installation tool that be used to rotate the locking nut.

FIG. 6A is a side view of an assembled device according to an embodimentof the present invention is an unexpanded, non-deployed state.

FIG. 6B is a side view of the device of FIG. 6A in an expanded state.

FIG. 6C is a side view of the device of FIG. 6B after a portion of thescrew of the device has been cut off.

FIG. 7A is a side view of an assembled device according to an embodimentof the present invention is an unexpanded, non-deployed state.

FIG. 7B is a side view of the device of FIG. 7A in an expanded state.

FIG. 7C is a side view of the device of FIG. 7B after a portion of thescrew of the device has been cut off.

FIG. 8 is a cross-sectional view of a device according to anotherembodiment of the present invention in an expanded state.

FIG. 9A is a side view of a device in an unexpanded non-deployed stateaccording to an embodiment of the present invention.

FIG. 9B is a side view of the device of FIG. 9A in an expanded stateaccording to an embodiment of the present invention.

FIG. 10A is a plan view of a device in an unexpanded non-deployed stateaccording to an embodiment of the present invention.

FIG. 10B is a plan view of the device of FIG. 10A in an expanded stateaccording to an embodiment of the present invention.

FIG. 11A is a perspective view depicting a device mounted to an elongatemember in an unexpanded non-deployed state and being inserted into an SIjoint according to an embodiment of the present invention.

FIG. 11B is a side view of the device of FIG. 11A in an expanded statein the SI joint according to an embodiment of the present invention.

FIG. 11C is a side view of the device of FIG. 11B in an expandeddeployed state in the SI joint after removal of the elongate member.

FIG. 12A is a plan view of a device in an unexpanded non-deployed stateaccording to an embodiment of the present invention.

FIG. 12B is a plan view of the device of FIG. 12A in an expanded stateaccording to an embodiment of the present invention.

FIG. 13A is a side view depicting a device mounted to an elongate memberin an unexpanded non-deployed state as it is being inserted into the SIjoint according to an embodiment of the present invention.

FIG. 13B is a side view of a device of the device of FIG. 13A positionedin the SI joint according to an embodiment of the present invention.

FIG. 13C is a side view of the device of FIG. 13B in an expanded statein the SI joint according to an embodiment of the present invention.

FIG. 13D is a side view of the device of FIG. 13C in an expandeddeployed state in the SI joint after removal of the elongate memberaccording to an embodiment of the present invention.

SUMMARY OF THE INVENTION

In an embodiment, the present invention provides a method of stabilizinga sacroiliac joint in a patient in need thereof. The method comprisesproviding a device that comprises an expandable body defining a cavityand at least one opening in communication with (i) the cavity and (ii)the outer surface of the body. The expandable body is generallyfabricated from a material that is rigid enough to withstand thecompressive and torsional forces accepted by the SI joint but flexibleenough to assume both an unexpanded configuration in a non-deployedstate and a radially expanded configuration in a deployed state. Themethod further comprises inserting the device into the sacroiliac joint.The device can be inserted percutaneously or via open surgery. Onceproperly positioned, the method further comprises expanding theexpandable body to engage the sacroiliac joint to securely seat theexpandable device in the sacroiliac joint. By being securely seated inthe sacroiliac joint, the device is not readily displaced by normalbodily movement. The method further comprises providing a bone materialin or one the expandable body of the device to permit fusion of thesacroiliac joint.

The methods of the present invention can be used to treat dysfunction ofthe SI joint resulting in destabilization, such as hypermobility, of thejoint. Such SI joint dysfunction can be can be caused by disease, age,injury or other factors.

DETAILED DESCRIPTION OF THE INVENTION

In general, the present invention provides methods of stabilizing thesacroiliac joint in a patient in need thereof using a device having anexpandable portion that engages the sacral and iliac surfaces of thesacroiliac joint. Specifically, referring to FIG. 1, the methods involvegenerating laterally opposing forces against the iliac and sacralsurfaces of the SI joint to securely seat a device 10 in a planegenerally parallel to the SI joint. Prior methods, in contrast, involveddisposing a bone screw perpendicular to the joint to direct compressiveforces against the iliac and sacral surfaces to draw the surfaces closertogether. The expandable portion of devices used in the methods of thepresent invention is either coated with or otherwise contains a bonematerial, such as bone graft or a substrate containing a bonemorphogenic protein, to facilitate fusion of the joint. By stabilizingthe sacroiliac joint, the methods of the present invention eliminate orreduce motion across the joint and fuse the sacrum and ilium bones atthe SI joint. The device used in methods of the present invention caninclude any biocompatible devices which have an expandable portion thatcan assume both an unexpanded and radially expanded position and thatare sized to fit in, but not necessarily expand, the SI joint in a fullydeployed position.

For example, referring to FIG. 2, in an embodiment, a device 10 that canbe used in methods of the present invention comprises an expandable body20 defining a cavity 25. In this embodiment, expandable body 20comprises a plurality of strips 26 that axially extend from a proximalend 27 to a distal end 28 of body 20 and that are capable of yieldinglaterally when compressed axially. Preferably, strips 26 are uniformlycircumferentially spaced apart. As seen in FIG. 1, the plurality ofstrips 26 define a plurality of axially extending openings or slits 30between adjacent ones of the plurality of strips 26, such openings orslits 30 being in fluid communication with cavity 25. However, otherembodiments of body 20 are also contemplated where body 20 defines atleast one opening extending from the outer surface of body 20 to theinner surface and therefore in communication with cavity 25 as well asthe exterior of body 20. Cavity 25 allows for receipt of a bone materialand openings 30 provide a pathway by which bone ingrowth can beachieved. In other words, when device 10 is in a fully deployedposition, expandable body 20 allows for bony ingrowth through openings30 to cavity 25, when the cavity is filled with a substance thatencourages bone growth.

In this embodiment, device 10 further comprises a screw 40 comprising ashaft 45 having a proximal end 46 and a distal end 47 and upon whichexpandable body 20 is mounted during use. In the embodiment illustratedin FIG. 2, shaft 45 is fully threaded. However, in other embodiments,shaft 45 can be partially threaded. Screw 40 further comprises apointed, cutting distal tip 50 extending from the distal end of shaft45. Distal tip 50 has a proximal face 51 that has a width W greater thanthe width W.sub.1 of the distal end of shaft 45 so as to accept theaxially compressive forces of expandable body 20 when device 10 is beingdeployed. Referring to FIG. 3, in this embodiment, proximal end 46 ofshaft 45 defines a proximal opening 52, distal end 47 defines a distalopening 55, and a hollow channel 60 extends between proximal end 46 anddistal end 47 and is in fluid communication with proximal opening 52 anddistal opening 55. Distal tip 50 also comprises a channel 13 inregistration with channel 60 and in fluid communication with distalopening 55 of shaft 45. Both channels 60 and 13 are sized to accommodatea guidewire, which can be used during insertion of device 10 into thepatient's body.

Proximal end 46 of shaft 45 can be configured to accept a distal end ofa driving tool to rotationally drive screw 40 through bone and into thesacroiliac joint. For example, referring to FIG. 4, a driving tool 101can be used which has a larger cylindrical section 155 with opposingmating flanges 151 a and 151 b (not shown) and a smaller diametercylindrical extension 146 extending from larger section 155. A springloaded ball detent 131 can be disposed on the distal end of extension146. Proximal end 46 of shaft 45 can define a pair of opposing slots 48a and 48 b, configured to receive opposing mating flanges 151 a and 151b on driving tool 101. Further, channel 60 of device 10 can be sized tofrictionally engage cylindrical extension 146 of driving tool 101. Atthe appropriate point in the surgical procedure when the device 10 isready to be installed, cylindrical extension 146 can be inserted intochannel 60 such that ball detent 131 resides in channel 60. Matingflanges 151 and 152 are aligned with slots 48 and the device can then bescrewed into place. Of course, other means of engaging a driving toolwith the proximal end of screw 40 can also be used such as othermale/female connections; threadable engagement; and/or interference orfrictional fit.

Referring back to FIG. 2, this embodiment of device 10 also includes alocking nut 65 to threadably engage shaft 45 of screw 40. Locking nut 65can also be configured to accept the distal end of a driving tool totighten nut onto shaft 45. For example, referring to FIG. 5, locking nut65 can have a hexagonal shaped outer surface 66 to engage a driver tool105 having a distal end having a complementary shaped inner surface 110.

Although in the above-described embodiments, the driving tools used torotate the screw and nut are separate devices, a single device can beused to rotate each component. Further, although in the above-describedembodiments, the devices used to rotate the screw and nut areindependently actuatable since one component is held stationary whilethe other component is urged distally or proximally in order to expandthe expandable body, in other situations it may be necessary to rotateboth screw and nut simultaneously in order to advance the device in thepatient's body. In such embodiments, the installation tools used torotate the screw may be a single device that rotate the components inconcert.

The components of the device can be fabricated from various materials toallow such components to operate according to their intended function.For example, the expandable body can be fabricated from any sterile,biocompatible material that is flexible enough such that it can becompressed when axial forces are applied thereto yet have sufficientcompressive strength to remain in an expanded configuration when fullydeployed for a long enough period of time to permit bone fusion. Forexample, expandable body can be fabricated from a deformable materialsuch as a flexible metal or elastomeric polymer. Non-limiting examplesof suitable materials include titanium, expandablepolytetrafluorethylene (ePTFE), or polyetheretherketone (PEEK). Thescrew and locking nut can be fabricated from a number of sterile,biocompatible materials such as a metal, a polymeric material, or aceramic. Non-limiting examples of a metal include stainless steel,cobalt-chrome or titanium alloys. Non-limiting examples of plasticsinclude a blend of polycaprolactone and polyglycolide, a blend ofpolylactide and polyglycolide, pure polydioxanone, poly(ethylene oxide),poly(butylene terephthalate), polyorthoester, or polyhydroxybutyrate. Incertain embodiments, the components of the device are fabricated frombiodegradable materials such as polycaprolactone, poly(L-lactide),polyglycol, poly(D,L-lactide), poly(D,L-lactide-co-glycol),poly(D,L-lactide-cocaptrolactone), polydioxanone, copolyoxalates andpolycarbonates, such as, for example,polyglycol-co-trimethylenecarbonate and poly(glutamine-co-leucine).

Furthermore, the components of the device can be completely separatecomponents or certain components can be integrally attached. Forexample, the expandable body can be fixedly attached to the distal sideof the locking nut, fixedly attached to the proximal surface of thedistal tip of the screw, or fixedly attached to both the distal side ofthe locking nut and the proximal surface of the distal tip of the screw.In other embodiments, the device can be fabricated as one single unitarypiece without separable components.

Referring to FIG. 6A, in an exemplary use of device 10, body 20 isplaced onto shaft 45 of screw 40 in an unexpanded, non-deployed state.As seen in this figure, body 20 has a generally elongated cylindricalconfiguration in this unexpanded state. Locking nut 65 is then threadedonto shaft 45 proximal to body 20. One or more driving tools are used torotationally drive both screw 40 and locking nut 65 into the sacroiliacjoint. Referring to FIG. 6B, once device 10 reaches the proper positionin the joint, screw 40 can be held stationary while locking nut 65 isrotated to move distally down shaft 45 of screw 40 in the direction ofthe arrow to urge body 20 against the proximally facing surface 51 ofdistal tip 50. Body 20 is thereby compressed and radially expands. Oncein an expanded configuration, body 20 engages the sacral and iliacsurfaces of the sacroiliac joint. As is seen in FIG. 6B, body 20 has agenerally oblong configuration in this expanded state. Once device 10 issecurely positioned, a portion of shaft 45 proximal to locking nut 65can then be cut or broken off as shown in FIG. 6C. Either prior to orafter placement of device 10 in the sacroiliac joint, a bone materialcan be placed in cavity 25 of body 20. Alternatively, a bone materialcan be pre-coated onto the outer surface of body 20. Eventually, apatient's body incorporates the bone material and device 10 becomesstructurally united with the joined bones.

Referring to FIGS. 7A-7C, in an alternative method of installing device10, instead of holding screw 40 stationary and rotating locking nut 65to move distally along shaft 45, locking nut 65 can be held stationaryand screw 40 rotated to move proximally in the direction of the arrow todraw expandable body 20 against locking nut 65, thereby compressing body20 and causing its radial expansion.

Referring to FIG. 8 in another embodiment, device 10 comprises anexpandable body 20 that is a balloon which defines a cavity 25. Incertain embodiments, the outer surface of expandable body 20 is coatedwith a bone material and in other embodiments, a bone material iscontained within cavity 20 of expandable body 20, in which caseexpandable body 20 is fabricated from a biodegradable material. Device10 further comprises an elongate member 41 comprising a shaft 42 uponwhich expandable body 20 is mounted and has a proximal end 56 and adistal end 43. In certain embodiments, elongate member 41 furthercomprises a pointed, cutting distal tip 54 extending from distal end 43of shaft 42 and having a closed distal end. Proximal end 56 of shaft 42defines a proximal opening 61 and a hollow channel 62 that extendsbetween proximal end 56 and distal end 43 and is in fluid communicationwith proximal opening 61. Hollow channel 62 can be sized to accommodatea guidewire, which can be used during insertion of device 10 into thepatient's body. Hollow channel 62 can also be used to deliver materialto cavity 25 of expandable body 20. For example, in certain embodiments,shaft 42 defines a plurality of apertures 72 in fluid communication withchannel 62 at one end and in fluid communication with cavity 25 atanother end. In embodiments where cavity 25 contains a bone material,apertures 72 allow for the bone material to be delivered through channel62 into cavity 25. In embodiments where the outer surface of expandablebody 20 is coated with a bone material, apertures 72 allow for aninfusate material, which solely functions to inflate body 20, to bedelivered through channel 62 to infuse cavity 25 and expand expandablebody 20. In other embodiments, the shaft can define a lumen(s) separatethan the hollow channel to deliver either an infusate or a bone materialto the cavity of the expandable body.

Referring to FIGS. 9A-9B, in an exemplary use of device 10, body 20 isdisposed on shaft 42 of elongate member 41 in an unexpanded, collapsedconfiguration. One or more driving tools are used to rotationally driveelongate member 41 into the sacroiliac joint. Such driving tools can besimilar to those described above or can have alternative designs so longas they can perform the function of delivering the device to the SIjoint. In certain embodiments, once device 10 reaches the properposition in the joint, a bone material is infused through channel 62into cavity 25 to expand body 20 such that body 20 abuts against thesacral and iliac surfaces of the SI joint. After time, expandable body20 biodegrades, releasing the bone material contained within cavity 25.In other embodiments, the outer surface of body 20 is coated with a bonematerial and an infusate is infused through channel 62 into cavity 25 toinflate body 20. In an expanded deployed state, the sacral and iliacsurfaces of the SI joint are exposed to the coating on body 20. Ineither embodiment, the SI joint is exposed to bone material facilitatingfusion of the joint.

In this embodiment, the expandable body is preferably fabricated from anon-compliant material such that the material elongates upon theapplication of pressure and takes the shape of the areas of the SI jointin which the expandable body is placed when fully inflated. Suitableballoon materials include elastomers, such as, for example, silicone,latex, or low durometer polyurethane (for example, a durometer of about80 A). Preferably, the expandable body, particularly in embodimentswhere cavity 25 is filled with bone materials but also in embodimentswhere the expandable body is coated with a bone material, is fabricatedfrom a biodegradable material such as a polylactic acid polymer, apolyvinyl acetate, an acrylonitrile or other biodegradable balloonmaterials described in WO/2006/001009, which is incorporated byreference herein.

Referring to FIGS. 10A and 10B, in other embodiments, device 10comprises a balloon expandable stent. Specifically, device 10 comprisesan expandable body 20 that has a tubular configuration similar to astent, and which defines a cavity 25. As seen in FIG. 11A, body 20comprises a first end 81, a second end 82 and a wall surface 74 disposedtherebetween. In this embodiment, wall surface 74 is formed by aplurality of intersecting elongate members 77 but other designs are alsopossible as described below. Expandable body 20 assumes a first diameterD in a relaxed state and a second diameter D′ upon the application of aradial force extending outwardly from the interior of cavity 25. Incertain embodiments, the outer surface of expandable body 20 is coatedwith a bone material and in other embodiments, a bone material iscontained within cavity 25 of expandable body 20.

Although in the embodiment illustrated in FIG. 10, expandable body 25comprises a plurality of intersecting elongate members 77, in otherembodiments, wall surface 74 can have a coil-like configuration, ahelical configuration or other configurations common in the balloonexpanding stent field including those described in U.S. Pat. No.4,733,665, which is incorporated by reference herein. For example, onedesign possibility is for the expandable body of the device to be asmall tube composed of collapsed metal struts linked to one another bylaser or spot welding or for the expandable body to be a metal tubewhere the collapsed struts are carved into the tube using any of avariety of means, including laser energy. Numerous other strut designsare possible that would permit balloon expansion of expandable body 20.

Referring to FIGS. 11A-11C, in an exemplary use of device 10, device 10can be collapsed down onto a folded balloon 12 mounted to an elongatemember 13 similar to the elongate member shown in FIG. 8. Device 10maintains this collapsed configuration, as seen in FIG. 11A, until it isaffirmatively expanded. Device 10 is inserted into the SI joint and onceproperly positioned, balloon 12 is inflated to an appropriate size,expanding device 12 to the desired diameter as seen in FIG. 11B. Balloon12 is then deflated and elongate member 13 withdrawn, leaving expandeddevice 10 in place within the SI joint as shown in FIG. 11C. Device 10remains in its expanded deployed state because of the deformation thatwas imparted to its structural elements during expansion. At any timeduring placement, a bone material can be inserted into cavity 25 ofexpandable body 20 or the outer surface of expandable body 20 can bepre-coated with a bone material. In either embodiment, the SI joint isexposed to bone material facilitating fusion of the joint.

The device can be fabricated from materials commonly used in themanufacture of balloon expandable stents such as stainless steel,polymeric or bioabsorbable materials. In preferred embodiments, thedevice is fabricated from a biodegradable material such as, for example,copolymers of L-lactide and/or .epsilon.-caprolactone.

Referring to FIGS. 12A and 12B, in another embodiment, device 10 is aself-expanding stent. Specifically, device 10 comprises a self-expandingbody 20 that is a tubular shaped coil of wire having a plurality ofhelical turns 14 and which defines a cavity 25. In this embodiment, body20 is fabricated from a shape memory alloy that can be manufacturedaccording to well known principles so that when heated to its transitiontemperature, it assumes a diameter that is approximately equal to thatof the SI joint so that device 10 can be securely fitted into the joint.Specifically, expandable body 20 assumes a first diameter D in a relaxedstate and a second diameter D′ upon radial expansion. Therefore, incontrast to the balloon-expandable device described above, device 10 ofthis embodiment is formed to assume a pre-determined diameter.

Referring to 13A-13D, in an exemplary use of device 10, the device isplaced securely over an elongate member 210 having a threaded, pointed,cutting distal tip 213 with a closed distal end. Similar to the elongatemember illustrated in FIG. 8, elongate member 210 in this embodiment candefine a hollow channel along the longitudinal axis thereof as well asside apertures 222 similarly defined along the longitudinal axis thereofand in communication with the channel at one end and the outer surfaceof the elongate member at the other end. The side apertures 222 permitexit of fluid delivered through the elongate member. As stated above,distal tip 213 can have a closed end so that fluid only exits the sideapertures. Device 10 can then be inserted into the SI joint as shown inFIG. 13A. Once at the proper position as seen in FIG. 13B, device 10 canbe heated to a temperature at which the nitinol alloy from which body 20is fabricated, reaches its transition temperature and austenitetranformation occurs as seen in FIG. 13C. This can be accomplished byinjecting a hot fluid through the channel of elongate member 210 toexpandable body 20 so as to bathe and trigger expansion of device 10.Once device 10 is in a fully expanded state, the elongate member can beretracted leaving device 10 in place as shown in FIG. 13D. At any timeduring placement, a bone material can be inserted into cavity 25 ofexpandable body 20 or the outer surface of expandable body 20 can bepre-coated with a bone material. In either embodiment, the SI joint isexposed to bone material facilitating fusion of the joint.

Another method that can be used to deliver a device that is aself-expanding stent to the SI joint involves mounting the stent on thedistal end of an elongate member and covering the stent with asurrounding sheath to maintain the stent in a compressed state. Theself-expanding stent can be implanted by advancing the elongate memberto the SI joint, withdrawing the sheath so that the stent canself-expand into the body lumen, and then withdrawing the elongatemember and sheath leaving the stent implanted.

The expandable body of the device in this embodiment can have designsother than those described above, including designs that are common inthe self-expanding stent field. For example, the expandable body cancomprise flexible interwoven metal wires or small metal rings welded toadjacent rings. Each ring in such a design can have a zigzagconfiguration. Both the interwoven and multiple zigzag ring designs canbe highly compressed to fit within a delivery sheath. Non-limitingexamples of self-expanding stents that can be used in the presentinvention are described in U.S. Pat. No. 5,554,181 and U.S. Pat. No.4,655,771, both of which are incorporated by reference herein.

The expandable body in this embodiment can be fabricated from a materialcommonly used in the manufacture of a self-expanding stent such asmetals or polymers. Non-limiting examples of a metal are stainlesssteel, silver and a nickel titanium alloy. Non-limiting examples ofpolymers are polyesters, polyurethanes, polycarbonates, polysulfides,polypropylenes, polyethylenes, and polysulfonates. In preferredembodiments, the material is biodegradable.

In any of the above embodiments, any of the various described componentscan include a radio-opaque, such as, for example, barium, tungsten,bismuth, tantalum, and tin to allow the components to be visualized viastandard imaging modalities.

Regarding the dimensions of devices used in the present invention, inmost embodiments, the expandable bodies of the devices are generallyfrom about 5 to 40 millimeters (mm) long and from about 5 to 20 mm widein an unexpanded state. In a preferred embodiment, the expandable bodiesare about 35 mm long and about 5 mm wide in an unexpanded state. In anexpanded state, the expandable bodies are generally from about 5 to 40mm long and from about 5 to 40 mm wide. In a preferred embodiment, theexpandable bodies are 20 mm long and 20 mm wide in an expanded state.

The bone material used in the above described embodiments can be a bonegraft material or a BMP. Bone graft materials are well known in the artand include both natural and synthetic materials. For example, the bonegraft material can be an autologous or autograft, allograft, xenograft,or synthetic bone graft. BMPs are also well known in the art and includeBMP-2, BMP-3, BMP-4, BMP-5, BMP-6 (VGR-1), BMP-7 (OP-1), BMP-8, BMP-9,BMP-10, BMP-11, BMP-12, BMP-13, BMP-14, BMP-15. Preferred BMPs are anyof BMP-2, BMP-3, BMP-4, BMP-5, BMP-6, and BMP-7. The bone material canalso include other therapeutic agents such as anti-microbial agents orantibiotics.

An exemplary surgical procedure to place a device of the presentinvention in the SI joint will now be described. The procedure can beperformed in a minimally invasive fashion under fluoroscopy. The patientis placed in the prone position and a small stab incision is made in theposterior superior iliac spine directly underneath the visible dimplesjust above the buttocks over the sacroiliac joint. The SI joint isvisualized under X-ray and a jam-sheaty needle is used to locate thearea for placement. A guidewire (such as a K-wire) is advanced throughthe needle. The joint is opened and cartilage is cleared using a reameror small channeling tool. The jam sheaty needle is removed and the guidewire is left in place. The device is inserted over the guide wire. Usinga screwdriver or other driving tool, the device is inserted into thejoint under fluoroscopy guided X-ray. When the ideal location isdetermined, the device is expanded under live fluoroscopy and stabilitychecked. The device can be filled with a bone material prior to or afterplacement. The guide wire is removed and the small stab incisionirrigated and closed. This procedure could also be preformed with anopen larger incision.

The foregoing description and examples have been set forth merely toillustrate the invention and are not intended as being limiting. Each ofthe disclosed aspects and embodiments of the present invention may beconsidered individually or in combination with other aspects,embodiments, and variations of the invention. Further, while certainfeatures of embodiments of the present invention may be shown in onlycertain figures, such features can be incorporated into otherembodiments shown in other figures while remaining within the scope ofthe present invention. In addition, unless otherwise specified, none ofthe steps of the methods of the present invention are confined to anyparticular order of performance. Modifications of the disclosedembodiments incorporating the spirit and substance of the invention mayoccur to persons skilled in the art and such modifications are withinthe scope of the present invention. Furthermore, all references citedherein are incorporated by reference in their entirety.

We claim:
 1. An implant for stabilizing a sacroiliac joint in a patientin need thereof comprising: a screw having a tip and a shaft, at least aportion of the shaft includes threads; an expandable body having adistal end, a proximal end and defining a cavity and at least oneopening in communication with (i) the cavity and (ii) an outer surfaceof the body, and the expandable body being fitted over at least aportion of the shaft of the screw with the distal end of the expandablebody capable of contacting the tip of the screw; a nut member, the nutmember capable of engaging the threaded portion and capable ofcontacting the proximal end of the expandable body; the device having anunexpanded configuration in a non-deployed state and a radially expandedconfiguration in a deployed state; wherein the implant is radiallyexpanded to engage the sacroiliac joint to securely seat the device inthe sacroiliac joint by rotating the nut member thereby compressing theexpandable body between the tip and the nut member.
 2. The implant ofclaim I, wherein placing a bone material on the expandable bodycomprises providing a device comprising an expandable body having anouter surface coated with a bone material.
 3. The implant of claim 1,wherein the at least one opening is a plurality of openings.
 4. Theimplant of claim 3, wherein the expandable body comprises a plurality ofstrips that extend from the proximal end to the distal end of the body,the plurality of strips defining a plurality of openings therebetween.5. The implant of claim 1, wherein the screw comprises: (a) a shafthaving a proximal end and a distal end and (b) a pointed, cutting distaltip extending from the shaft, wherein the expandable body is mounted onthe shaft.
 6. The implant of claim 5, wherein the shaft defines achannel extending from the proximal end to the distal end of the shaft.7. The implant of claim 5, wherein the device further comprises alocking nut sized to threadably engage the shaft of the screw.
 8. Theimplant of claim 1, wherein the expandable body is fabricated from abiodegradable material.
 9. The implant of claim 5, wherein the screw isfabricated from a biodegradable material.
 10. The implant of claim 7,wherein the locking nut is fabricated from a biodegradable material. 11.The implant of claim 1, wherein the bone material is a bone graft. 12.The implant of claim 1, wherein the bone material is a bonemorphogenetic protein.
 13. The implant of claim 1, wherein the device isinserted into the sacroiliac joint percutaneously.
 14. The implant ofclaim 1, further comprising placing a bone material within the cavity ofthe expandable body of the device to permit fusion of the sacroiliacjoint.
 15. An implant for stabilizing a sacroiliac joint comprising: ascrew having a tip and a shaft, at least a portion of the shaft includesthreads; an expandable body having a distal end, a proximal end anddefining a cavity and at least one opening in communication with (i) thecavity and (ii) an outer surface of the body, and the expandable bodybeing fitted over at least a portion of the shaft of the screw with thedistal end of the expandable body capable of contacting the tip of thescrew; a nut member, the nut member capable of engaging the threadedportion and capable of contacting the proximal end of the expandablebody; the device having an unexpanded configuration in a non-deployedstate and a radially expanded configuration in a deployed state; whereinthe implant is radially expanded to engage the sacroiliac joint tosecurely seat the device in the sacroiliac joint.
 16. The implant ofclaim 15, wherein placing a bone material on the expandable bodycomprises providing a device comprising an expandable body having anouter surface coated with a bone material.
 17. The implant of claim 15,wherein the at least one opening is a plurality of openings.
 18. Theimplant of claim 17, wherein the expandable body comprises a pluralityof strips that extend from the proximal end to the distal end of thebody, the plurality of strips defining a plurality of openingstherebetween.
 19. The implant of claim 15, wherein the screw comprises:(a) a shaft having a proximal end and a distal end and (b) a pointed,cutting distal tip extending from the shaft, wherein the expandable bodyis mounted on the shaft.
 20. An implant for stabilizing a sacroiliacjoint comprising: a screw having a tip and a shaft, at least a portionof the shaft includes threads; an expandable body having a distal end, aproximal end and defining a cavity and at least one opening incommunication with (i) the cavity and (ii) an outer surface of the body,and the expandable body being fitted over at least a portion of theshaft of the screw with the distal end of the expandable body capable ofcontacting the tip of the screw; a nut member, the nut member capable ofengaging the threaded portion and capable of contacting the proximal endof the expandable body; the device having an unexpanded configuration ina non-deployed state and a radially expanded configuration in a deployedstate; and a locking nut sized to threadably engage the shaft of thescrew; wherein the implant is radially expanded to engage the sacroiliacjoint to securely seat the device in the sacroiliac joint by rotatingthe nut member thereby compressing the expandable body between the tipand the nut member,